Drugs Metabolized by Hepatic Microsomal Enzymes

Gemifloxacin is not an inhibitor of cytochrome P-450 (CYP) isoenzymes; pharmacokinetic interaction unlikely.

Antacids

Pharmacokinetic interaction (decreased absorption of gemifloxacin). Gemifloxacin should be taken at least 2 hours before or 3 hours after antacids that contain aluminum or magnesium. (See Dosage and Administration: Administration.) Antacids containing calcium or calcium supplements have no clinically important pharmacokinetic interaction with gemifloxacin.

Didanosine Pharmacokinetic interaction; didanosine chewable/dispersible buffered tablets, buffered powder for oral solution, or pediatric powder for oral solution prepared as an admixture with antacid may substantially decrease gemifloxacin absorption. Gemifloxacin should be taken at least 2 hours before or 3 hours after these buffered didanosine preparations.

Theophylline Pharmacokinetic interaction unlikely.

Warfarin Pharmacologic interaction unlikely.

However, because some quinolones have been reported to enhance the effects of warfarin and its derivatives, prothrombin time or other suitable coagulation tests should be monitored closely if a quinolone anti-infective agent is administered with warfarin or its derivatives.